Tuning Sub Amp

Been trying to get my sub amp tuned in good and I have a question.

I have the Pioneer AVH-P4200DVD which has a built in sub crossover and is connect to an Alpine PDX 1.600 which also has a built in crossover. I can't diable/turn off one or the other, so which should I use and what should I have the other set at?

Thanks,
Kevin

 

I'd use the one on the headunit and then set the one on the amp as high as it will go so it's really not being used.

 

not sure if this helps your situation but what I do is set my hi pass on my deck to 150 hz and my low pass on my amp to 150 hz then the subs take care of all the bass and my speakers will last for ever.

using both cross overs on your deck and your amp wont hurt anything

 

I would set the low pass on the amp to 200 hz and play with the low pass on the hu, every vehicle is different and every hu/amp/sub set up is different and the best way to find what works with yours is to play with it.
What box are you using?